1. Field of the Invention
The present invention relates to a display device, and more particularly to a technique which is effectively applicable to a display device having a common electrode driver circuit which drives common electrodes.
2. Description of the Related Art
For example, in an active-matrix-type liquid crystal display device which uses thin film transistors (TFT) as active elements, on a liquid-crystal-side surface of one substrate out of substrates which are arranged to face each other in an opposed manner with liquid crystal sandwiched therebetween, pixel regions each of which is surrounded by scanning signal lines which extend in the x direction and are arranged parallel to each other in the y direction and video signal lines which extend in the y direction and are arranged parallel to each other in the x direction are formed. The pixel region includes a pixel-use transistor (TFT) which is operated in response to the supply of a scanning signal from the scanning signal line.
The liquid crystal display device includes a vertical driver circuit which supplies a scanning signal to the respective scanning signal lines, and a horizontal driver circuit which supplies a video signal to the respective video signal lines, and these driver circuits respectively include a shift register circuit.
On the other hand, there has been also known a polysilicon-type liquid crystal display device in which a semiconductor layer of a thin film transistor which constitutes the above-mentioned active element is made of polycrystalline silicon (polysilicon). In such a polysilicon-type liquid crystal display device, the thin film transistor (for example, MOS transistor) which constitutes the vertical driver circuit and the horizontal driver circuit is also formed on the above-mentioned surface of one substrate in the same step as the thin film transistors which constitutes the active elements.
For example, Japanese Patent Laid-Open No. 2007-156054 (patent document 1) discloses a related art of the present invention. That is, patent document 1 discloses a liquid crystal display device which includes a single-channel (n-MOS) common electrode driver circuit in a vertical driver circuit.